Many diseases of the central nervous system (CNS) are characterized by the devastating loss of neurons. Several approaches have been investigated to determine whether they could either halt or reverse this neuronal loss including the introduction of neurotrophic factors as well as transplantation of neural stem cells to provide a source of new neurons for reinnervation of the CNS. Recently, adult mesenchymal stem cells (MSCs) have been shown to have the potential to take on neuronal and glial properties when treated with neurotrophic factors in cell culture. Moreover, our own preliminary studies have demonstrated that glial-derived neurotrophic factor (GDNF) treated adult MSCs gain a sensitivity to the neurotransmitter glutamate. These studies suggest that adult MSCs have the ability to take on neuronal and/or glial properties suggesting a potential avenue for treatment for certain neurological disorders: the patient could supply their own MSCs which, after treatment with appropriate neurotrophic factors in culture, could be transplanted into the CNS where they would have the potentia to differentiate into neurons and ameliorate the symptoms of the disorder. Using adult MSCs we will determine the mechanisms of GDNF-induced calcium signaling, and will test the hypothesis that GDNF induces neuronal differentiation of stem cells as assayed by calcium signaling in response to the neurotransmitter, glutamate. We will ask whether the GDNF-induced calcium signal is essential for neuronal differentiation and whether MSCs that are transplanted into the retina, morphologically and functionally integrate into the retinal circuitry. Using confocal imaging together with UV photolysis and photo-release of caged glutamate to probe the circuitry of the retina we will test the hypothesis that GDNF treatment of adult-derived mesenchymal stem cells causes neuronal differentiation, and the ability of MSCs to integrate into functional circuity of the CNS. By mechanistically determining the regulation of the neuronal glutamatergic phenotype we will be able to design rational approaches to differentiate adult MSCs along neuronal pathways with the long-term objective of gaining functional integration of these treated cells in the CNS.